Flowmeters

ABSTRACT

A fluid flowmeter which includes a fluidic oscillator with feedback loops from its side walls to its control nozzles. At the junctions between the feedback loops and the side walls of the oscillator the feedback loops are arranged at an angle such that they do not face into the direction of flow of the fluid stream through the oscillator.

United States Patent [1 1 Grant et al.

[4 1 Sept. 2, 1975 [22] Filed:

[ FLOWMETERS [75] Inventors: John Grant; Andrew John Cox, both of Warrington, England [73] Assignee: United Kingdom Atomic Energy Authority, London, England Mar. 29, 1974 [21] Appl. No.: 456,267

[30] Foreign Application Priority Data Apr. 5, 1973 United Kingdom 16435/73 [52] US. Cl. 73/194 B; 137/835 [51] Int. Cl. GOIF l/20 [58] Field of Search 73/194 B; 137/835 [56] References Cited UNITED STATES PATENTS 3,273,377 9/1966 Testerman et al. 73/23.l

3,373,600 3/1968 Taplin 137/835 3,599,653 10/1971 Clayton 137/835 3,614,964 10/1971 Chen 137/835 FOREIGN PATENTS OR APPLICATIONS 1,225,570 3/1971 United Kingdom 73/194 B Primary Examiner-Herbert Goldstein Attorney, Agent, or Firm-Larson, Taylor & Hinds ABSTRACT A fluid flowmeter which includes a fluidic oscillator with feedback loops from its side walls to its control nozzles. At the junctions between the feedback loops and the side walls of the oscillator the feedback loops are arranged at an angle such that they do not face into the direction of flow of the fluid stream through the oscillator.

2 Claims, 2 Drawing Figures FLOWMETERS BACKGROUND OF THE INVENTION This invention relates to flowmeters of the kind using a fluidic oscillator, that is a device which produces oscillations when it is energised by a flow of fluid.

Essentially a fluidic oscillator has an interaction chamber with a main fluid inlet nozzle, diverging side walls to which a fluid stream issuing from the nozzle can attach (attachment walls) and control nozzles for exerting fluid pressure on the fluid stream and thereby directing the stream from one side wall to the other; a splitter may be provided to physically divide the flow. Feedback loops may be provided from the diverging side walls to the control nozzles. The purpose of these feedback loops is to create at the control nozzles fluid pressures which will effect switching of the fluid stream between the side walls and for use in a flowmeter (where the oscillations are desired to be proportional to the flow rate) the geometry of the oscillator is such that fluid flow through the control nozzles is established by bulk flow of the fluid in the feedback loops rather than by fluid wave effects. Previously the momentum of the fluid stream has been used to create in the feedback loops fluid pressures responsive to the dynamic pressure of the fluid stream and the junctions between the side walls and the feedback loops have been made at an appropriate angle to bring this about, that is at an angle such that the feedback loops face into the direction of flow of the fluid stream at the junctions.

SUMMARY OF THE INVENTION According to the present invention a fluid flow meter includes a fluidic oscillator with feedback loops from its side walls to its control nozzles and the feedback loops at the junctions with the side walls are either at right angles to the side walls or at an angle such that the feeback loops face away from the direction of flow of the fluid stream through the oscillator.

By means of the invention fluid pressure in the feed back loops is made responsive only to the static pressure of the flulid stream and it has been found that this can lead to a better signal wave shape from the oscillator and improve the linearity of a flowmeter.

The position of the feedback loop junctions with the side walls is determined with reference to the static pressure profiles down the side walls of the oscillator. It has become customary in previous oscillators to provide restrictions downstream of the feedback loop junctions and the size and location of such restrictions may be chosen to optimize the static pressure profiles in the present oscillator. The linearity of a flowmeter in accordance with the invention and the strength and shape of its oscillations depend on these profiles. Re strictions may however not be necessary.

DESCRIPTION OF THE DRAWINGS By way of example a fluidic oscillator in accordance with the invention will now be described with reference to the accompanying drawings wherein FIG. 1 is an isometric view and FIG. 2 is a plan view.

DESCRIPTION OF A PREFERRED EMBODIMENT The drawings show a fluidic oscillator, with cover plate removed having an interaction chamber 1, a main fluid inlet nozzle 2, diverging side walls 3 and control nozzles 4. A splitter body 5 is provided to physically divide the flow from the interaction chamber 1. Feedback loops 6 are provided from the diverging side walls 3 to the control nozzles 4. At the junctions 7 between feed back loops 6 and the side walls (attachment walls) 3 the loops face away from the direction of flow of fluid through the oscillator. Restrictions 8 are provided downstream of the junctions 7.

A fluid oscillator in accordance with the invention may be used in a flowmeter in the ordinary way by measuring the frequency of oscillation (see, for example, US. Pat. No. 3,690,171 Mass flow may be determined if both amplitude and frequency of oscillation are measured and integrated in the manner of copending German Pat. application P23 14 163.1, opened to public inspection Oct. 4, 1973 and corresponding to copending US. Pat. application 341,080 filed Mar. 14, 1973.

We claim:

1. In a fluid flow meter including a fluidic oscillator with means for measuring the frequency of oscillation, the oscillator including feedback loops from its attachment walls to its control nozzles, in which oscillations are dependent on bulk flow through the feedback loops rather than by fluid wave effects, the improvement such that at the junctions between the feedback loops and the attachment walls the feed back loops are at right angles or less to the upstream portions of the attachment walls.

2. Apparatus as claimed in claim 1 wherein at said junctions said feedback loops face away from the direction of flow of the fluid stream through the oscillator.

l= l =l 

1. In a fluid flow meter including a fluidic oscillator with means for measuring the frequency of oscillation, the oscillator including feedback loops from its attachment walls to its control nozzles, in which oscillations are dependent on bulk flow through the feedback loops rather than by fluid wave effects, the improvement such that at the junctions between the feedback loops and the attachment walls the feed back loops are at right angles or less to the upstream portions of the attachment walls.
 2. Apparatus as claimed in claim 1 wherein at said junctions said feedback loops face away from the direction of flow of the fluid stream through the oscillator. 